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A $5.25 \%$ solution of a substance is isotonic with a $1.5 \%$ solution of urea $\left(\right.$ molar mass $=60 \mathrm{~g} \mathrm{~mol}^{-1}$ ) in the same solvent. If the densities of both the solutions are assumed to be equal to $1.0 \mathrm{~g} \mathrm{~cm}^{-3}$, molar mass of the substance will be
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$210.0 \mathrm{~g} \mathrm{~mol}^{-1}$
$210.0 \mathrm{~g} \mathrm{~mol}^{-1}$
Solutions with the same osmotic pressure are isotonic
Let the molar mass of the substance be $M$ $\pi_1=\mathrm{C}_1 \mathrm{RT}=\mathrm{C}_2 \mathrm{RT}=\pi_2$
So, $\mathrm{C}_1=\mathrm{C}_2$
As density of the solutions are same
So $\frac{5.25}{M}=\frac{15}{60}$
$M=\frac{5.25 \times 60}{1.5}=210$
Hence (D) is correct
Let the molar mass of the substance be $M$ $\pi_1=\mathrm{C}_1 \mathrm{RT}=\mathrm{C}_2 \mathrm{RT}=\pi_2$
So, $\mathrm{C}_1=\mathrm{C}_2$
As density of the solutions are same
So $\frac{5.25}{M}=\frac{15}{60}$
$M=\frac{5.25 \times 60}{1.5}=210$
Hence (D) is correct
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